1. Field of the Invention
The present invention relates generally to a method for controlling heat dissipation of an electronic device, such as a central processing unit of a computer, and in particular to a method for controlling heat dissipation of the electronic device based on the temperature of the electronic device.
2. Description of the Prior Art
It is known that electronic devices, such as a microprocessor or a central processing unit (CPU) of a computer system, must operate in a predetermined range of temperature. Over-temperature causes malfunction of the electronic device. Since the electronic device generates heat when operating, it is necessary to properly remove or dissipate the heat generated during the operation of the electronic device in order to maintain proper operation thereof.
Conventionally, a fan is generally mounted to an electronic device for generating airflow to induce force convection to the electronic device in order to remove heat generated by the electronic device. The rotational speed of the fan is generally designed to be constant that meets the full load operation thereof. Thus the airflow induced by the fan and the amount of heat removed by the airflow per unit time are fixed. This leads to unnecessary consumption of electrical power energy when the electronic device does not have such a high temperature that requires the full load operation of the fan.
Since power energy is generally limited and is thus a valuable resource of a portable electronic device, such as notebook computer or portable computer, the unnecessary power consumption reduces the operation time period that a battery of the notebook computer can support.
A stepwise approach is known in controlling the operation of a heat dissipation fan in prior art. The approach divides the operation of the fan into a number of stepwise levels each associated with a predetermined rotational speed of the fan. When the operating temperature of the electronic device reaches a lower bound of one specific level, the fan is controlled to operate at a rotational speed associated with the specific level. The lower bound of one level is the upper bound of the next lower level whereby when the temperature drops below the lower bound, the rotational speed of the fan is reduced to a value corresponding to the next lower level. Thus, the rotational speed of the fan jumps back and forth between successive levels when the temperature of the electronic device fluctuates. Such a sudden change in rotational speed of the fan causes undesired noise.
In addition, although the prior art stepwise approach reduces unnecessary power consumption, since the rotational speed of the fan maintains fixed in a given level between the upper and lower bounds thereof, there is still an unnecessary waste of power.
For certain industrial applications of computers, the electronic device operates at a very heavy load condition. This generates a huge amount of heat during the operation of the electronic device. Such a huge amount of heat can sometimes not be timely removed by the fan. Other method must be employed to reduce the amount of heat generated by the electronic device in order not to cause undesired damage to the electronic device. One feasible way is to decrease the clock frequency of the electronic device, which effectively reduces the operation load of the electronic device and thus remove the heat generated by the electronic device.
Thus, the primary object of the present invention is to provide a method for controlling heat dissipation of an electronic device by a fan assembly wherein the rotational speed of the fan is changed in proportion to the temperature change of the electronic device in a stepless fashion whereby no undesired noise occurs in changing rotational speed of the fan.
Another object of the present invention is to provide a method for controlling heat dissipation of an electronic device by a fan assembly whereby unnecessary power consumption is reduced.
A further object of the present invention is to provide a method for controlling heat dissipation of an electronic device by means of controlling a fan assembly to induce a force convection to remove heat generated by the electronic device and decreasing the clock frequency of the clock signal supplied to the electronic device so as to reduce the amount of heat generated by the electronic device thereby effectively maintaining the temperature of the electronic device in an acceptable range.
To achieve the above objects, in accordance with the present invention, a method for controlling heat dissipation of an electronic device, such as a microprocessor or a central processing unit, with the aid of a heat dissipation fan is provided. The method mainly comprises the following steps: detecting the temperature of the electronic device; comparing the temperature of the electronic device with the maximum reference temperature; rotating the fan in proportion to the temperature of the electronic device when the temperature of the electronic device is below the maximum reference temperature; rotating the fan at a maximum rotational speed when the temperature of the electronic device is beyond the maximum reference temperature; comparing the temperature of the electronic device with the slowing-clock starting reference temperature; rotating the fan at a maximum rotational speed and supplying a slower clock frequency with respect to the regular clock frequency of the clock signal to the electronic device when the temperature of the electronic device is beyond both the maximum reference temperature and the slowing-clock starting reference temperature; and maintaining the maximum rotational speed of the fan and supplying the slower clock frequency of the clock signal to the electronic device until the temperature of the electronic device drops below the slowing-clock ending reference temperature.
Preferably, the fan is turned off when the detected temperature of the electronic device is below a preset minimum reference temperature that is smaller than the maximum reference temperature.
Controlling the rotational speed of the fan in proportion to the temperature of the electronic device avoids sudden change of the fan speed and thus eliminating noise caused thereby. In addition, slowing down the clock frequency of the clock signal supplied to the electronic device effectively reduces the amount of heat generated by the electronic device and thus allowing the temperature of the electronic device to be brought down to proper working temperature thereof in case the fan itself is not sufficient to remove heat from the electronic device.